1. Field of the Invention
The present invention is broadly concerned with improved potassium sulfate salt products having enhanced water solubility permitting them to be used with greater efficiency as liquid, spray-on fertilizer products. More particularly, it is concerned with such improved potassium products, as well as a method of producing the same, wherein potassium sulfate is mixed with water and an appropriate surfactant and optional defoamer and subjected to heating to a temperature of from about 100.degree.-210.degree. F.; the solution, when cooled, exhibits a significantly increased potassium sulfate solubility as compared with untreated potassium sulfate solutions.
2. Description of the Prior Art
Potassium sulfate, potassium chloride and potassium nitrate are all used as fertilizer products to a greater or lesser degree. Potassium chloride is the most widely used potassium salt, but is inapplicable for chloride and/or salt-sensitive crops such as tobacco, fruits, vegetables and turfs. However, KCl has a significant water solubility on the order of 14-16% as K.sub.2 O, and therefore this salt is often applied as a liquid.
Potassium sulfate (commonly referred to in the trade as sulfate of potash or SOP) is a premium fertilizer product. Certain grades of SOP, particularly those manufactured from the brine of the Great Salt Lake, are especially valuable products because they are essentially free of chlorides. Therefore, such products are admirably suited for use on chloride and/or salt-sensitive crops and the like. A drawback of SOP, however, is that in its natural state it is significantly less soluble in water than KCl, having an ambient temperature solubility of about 4-6% by weight as K.sub.2 O. This relatively low water solubility has inhibited the use of K.sub.2 SO.sub.4 as a liquid fertilizer product, despite its otherwise significant advantages.
Potassium nitrate is more soluble than SOP, normally about 9-11% by weight as K.sub.2 O, but is a very expensive product as compared with KCl or K.sub.2 SO.sub.4. Nevertheless, it has achieved some commercial utility as a liquid fertilizer source, owing at least in part to its low salt index.
It will of course be appreciated that enhancement of the solubility of potassium sulfate salts would represent a significant advance. Such an improvement would mean that more concentrated solutions could be prepared and applied, thereby lessening preparation, storage and transportation costs associated with the liquids.